Conventionally, carbon materials such as graphite, activated carbon, carbon nanofibers, or carbon nanotubes are widely used as capacitor electrode materials from an environmental aspect.
For example, the following Patent Literature 1 discloses an electrode of an electrochemical capacitor comprising a doped carbon material and two conductive materials having different particle sizes. In Patent Literature 1, it is described that an electrochemical capacitor having low resistance and high output can be produced by using an electrode obtained by using a doped carbon material as an active material and adding two conductive materials having different particle sizes between the above active materials.